Sunday/Monday Storm System Potential. Heavy Rain or Snow?

Good evening everyone. In my last article here - I talked about the potential for a bigger storm system to develop and affect Illinois on Sunday. We're still seeing this system appear on the models, and others have taken notice too. 

In fact, I've already noticed a couple social media posts calling for a big snowstorm. While the system certainly carries the potential, there are a couple noteworthy things to point out at this time. 

1 - Models still disagree on the placement and timing. Ill show below, but models still aren't in agreement on when this potential system will arrive. Some show Sunday, others Monday. 

2 - The track could change drastically. One thing thats so hard about forecasting winter storms is even a 10 mile shift in the storm center can change the amount of snow someone receives by a great deal, or even mean the difference between seeing any snow at all VS just rain. 

3 - It could still be too warm to snow. Ahead of the system, rapid warm air advection will take place. In fact, if certain forecasts pan out, much of IL could see temperatures in the 50s and 60s the day before. Cold air will filter around the backside, but will it be cold enough to snow? Some models say yes, others say barely. 

So at thit, we continue to closely monitor the evolving forecast to get a better idea of what may happen. All we need for you to know is that something still appears to be brewing in the Sunday/Monday timeframe. 

A first guess by me? Illinois will see mostly a rain event from this one, but these systems have a history of appearing too far to the north and west on the models when we are 5-7 days away, and a southward shift in the forecast track - which would put us at a bigger risk for snow - would not surprise me at all. 

So lets take a look at some models and what we are seeing. First the GFS which has been pretty consistent in showing Sunday development. This seems like a good bet at this time. 

But then we have the GDPS which shows a Monday system. At least they are both consistent in the strength and location, so there is that. 

Here is a look at what we call an ensemble plot. Basically the model, in this case the GEFS is ran multiple times to see what the outcomes are. Here we can see many of them develop a storm, but with varying intensity and location. At this range this is pretty good agreement actually and confidence begins to increase. 

And last but not least, everyone's favorite. A snowfall map. Given the current expected track it would seem most of the heavy snow targets Iowa and Wisconsin, but it is pretty close to our border. This is why we'll be watching the storm track closely. Shift it south or east by 25 miles and at least northwest Illinois could be in for a heavy snow. Unfortunately given the warm, wet nature of this system it could be that slushy heart attack type snow. This will not be a particularly cold system. 

So like we always say everyone, stay tuned for the ever changing updates to the forecast! Especially as the days draw near. 

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Once again a Happy Thanksgiving and safe travels to all!

​-ALUCIO